Golf ball including a blend of highly neutralized acid polymers and method of manufacture

ABSTRACT

A golf ball having an inner core layer, an outer core layer enclosing the inner core layer, and a cover layer enclosing the outer core layer. The inner core layer includes a blend of a first highly neutralized acid polymer having a first Vicat softening temperature and a first specific gravity, a second highly neutralized acid polymer having a second Vicat softening temperature and a second specific gravity, and an ionomer-based masterbatch comprising an additive and an ionomer resin having a third Vicat softening temperature and a third specific gravity. The absolute values of the differences among the Vicat softening temperatures is no more than about 15° C. and the absolute value of the difference between the specific gravities is no more than about 0.015. The cover layer may include an inner cover layer enclosing the outer core layer and an outer layer enclosing the inner cover layer.

This application is a continuation of U.S. patent application Ser. No.13/194,094, filed Jul. 29, 2011, which application is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a golf ball including a blend of highlyneutralized acid polymers. The invention also relates to a golf ballincluding a blend of highly neutralized acid polymers with additives inan ionomer-based masterbatch. The invention also relates to a method ofmanufacturing products, particularly golf balls, including a blend ofhighly neutralized acid polymers and an ionomer-based masterbatchcontaining additives, and to a method for making the blend.

2. Description of Related Art

Golf balls are important sporting goods that have changed with changesin technology. For example, balls were first made of wood, and then bystuffing boiled, softened feathers into a leather sack. The sacktypically was painted white, and would tighten upon drying. However,because the feather ball tended to absorb moisture and to split, manyballs were required to play a round. Also, these feather balls wereexpensive as compared with wooden balls.

Both feather and wooden balls were in use until the gutta percha ballwas made. The gutta percha ball was relatively inexpensive and easilymanufactured. Also, the gutta percha ball was fairly durable, ascompared with the feather ball, performed well because the surface couldeasily be roughened to improve flight characteristics, and so becamepopular. However, the ball exhibited a tendency to break up in flight.

Golf balls comprising other elastic materials then were developed. Forexample, a golf ball having a rubber core and an elastic thread woundtightly around the core was developed. The winding was covered withgutta percha at first, but later with balata. However, balata-coveredgolf balls often are damaged by players who are less skilled at strikingthe ball. Thus, tougher covers were developed, including in particularcovers comprising a Surlyn® compound or a polyurethane compound.

The interior structure of the golf ball also has advanced, with plasticsand polymeric materials having properties and characteristicsappropriate for manufacture of high-quality, high-performance,affordable golf balls. In particular, polymeric materials havingproperties and characteristics appropriate for golf ball manufacturehave been developed. Such polymeric materials include polyurethanes andionomeric materials, including highly neutralized acid polymers. Blendedmaterials also are used to manufacture other products.

Blends of materials polymeric often contain other compositions,typically called additives, that adjust properties and characteristicsof golf balls and other products to achieve properties andcharacteristics that may not be available from a single material or fromthe polymers alone. However, many material blends that manufacturersseek to make are difficult, if not impossible, to make successfullybecause the components are not compatible or are not easily combined. Inparticular, highly neutralized acid polymers typically are difficult toblend, and some additives do not blend easily with highly neutralizedacid polymers.

Therefore, there exists a need for a golf ball comprising a layer havingproperties and characteristics obtained by blending polymeric materialswith additive compositions. Further, there exists a need for method ofmanufacturing products, particularly golf balls, including a blend ofhighly neutralized acid polymers and additives that are difficult tocombine with highly neutralized acid polymers, and for a method forblending highly neutralized acid polymers with such additives.

SUMMARY OF THE INVENTION

In an aspect, the invention relates to a golf ball comprising a blend ofhighly neutralized acid polymers. In particular, the blend comprises anionomer-based masterbatch. A golf ball layer includes a blend of a firsthighly neutralized acid polymer having a first Vicat softeningtemperature and a first specific gravity, a second highly neutralizedacid polymer having a second Vicat softening temperature and a secondspecific gravity, and an ionomer-based masterbatch comprising anadditive and an ionomer resin having a third Vicat softeningtemperature. The absolute values of the differences among the Vicatsoftening temperatures is no more than about 15° C. and the absolutevalue of the difference between the specific gravities is no more thanabout 0.015.

In another aspect, the invention relates to a method of manufacturing aproduct, particularly a golf ball, comprising a blend of highlyneutralized acid polymers. In particular, the invention relates to amethod of manufacturing a golf ball comprising a blend of highlyneutralized acid polymers and an ionomer-based masterbatch, and to amethod of making the blend, which method includes blending highlyneutralized acid polymers with the ionomer-based masterbatch comprisingadditives, controlling the differences in softening temperatures of thehighly neutralized acid polymer and ionomer components of the blend, andcontrolling the difference in specific gravities of the highlyneutralized acid polymers.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingdrawings and description. The components in the figures are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention. Moreover, in the figures, likereference numerals designate corresponding parts throughout thedifferent views.

FIG. 1 shows a representative golf ball in accordance with thisdisclosure having a two-piece construction comprising a core layer and acover layer;

FIG. 2 shows a second representative golf ball in accordance with thisdisclosure having a three-piece construction comprising a core layer, aninner cover layer, and an outer cover layer;

FIG. 3 shows a third representative golf ball in accordance with thisdisclosure having a three-piece construction comprising an inner corelayer, an outer core layer, and a cover layer; and

FIG. 4 shows a fourth representative golf ball in accordance with thisdisclosure having a four piece construction comprising an inner corelayer, an outer core layer, an inner cover layer, and an outer coverlayer.

DETAILED DESCRIPTION

Generally, the invention relates to a golf ball including a blend ofhighly neutralized acid polymers and additives. The invention relates toa golf ball comprising a blend of highly neutralized acid polymers. Inparticular, the blend comprises an ionomer-based masterbatch. A golfball layer includes a blend of a first highly neutralized acid polymerhaving a first Vicat softening temperature and a first specific gravity,a second highly neutralized acid polymer having a second Vicat softeningtemperature and a second specific gravity, and an ionomer-basedmasterbatch comprising an additive and an ionomer resin having a thirdVicat softening temperature and a third specific gravity. The absolutevalues of the differences among the Vicat softening temperatures is nomore than about 15° C. and the absolute values of the differences amongthe specific gravities are no more than about 0.015.

The invention also relates to a method of manufacturing a golf ballcomprising a blend of highly neutralized acid polymers and additives byintroducing additives that are difficult to blend with highlyneutralized acid polymer as part of the masterbatch, controlling thedifferences in Vicat softening temperatures of the highly neutralizedacid polymers and ionomer resin of the blend, and controlling thedifferences in specific gravities of the highly neutralized acidpolymers and ionomer resin of the blend, and to the method of making theblend.

Blending highly neutralized acid polymers can be difficult. Theproperties and characteristics of ionic polymers such as highlyneutralized acid polymers can cause difficulty in blending. The skilledpractitioner recognizes that highly neutralized acid polymers act likecross-linked polymers because the neutralized carboxylate moieties,i.e., the polar parts of the molecule, tend to cluster together in theotherwise non-polar polymer. However, the clusters tend to separate whenheated, thus causing the compound to soften like a thermoplasticmaterial and to provide an opportunity to process the heated material.

Thus, to form a blend, the compounds that make up a blend of highlyneutralized acid polymers typically will be heated to take advantage ofthe resultant thermoplasticity. However, the compounds often will remaindifficult to blend, because the component polymers often do not softenunder the same conditions and thus will be difficult to process.

Controlling the differences between the Vicat softening temperatures andthe specific gravities of the highly neutralized acid polymers formingthe blend ameliorates processing problems encountered when blending thematerials and yields an essentially homogeneous blend. These processingproblems include formation of gas from a polymer that has a lowermelting temperature than the melting temperature of the other polymersin the blend and stratification of molten material. Gas may be formed ifa highly neutralized acid polymer is over-heated to the higher softeningtemperature required by the other components of the blend. Formation ofgas during processing causes voids in the processed product. Adifference in specific gravities makes it difficult to control themixing ratio, leading to stratification and heterogeneity in a product.Stratification and heterogeneity in the molded product also is a defectin the processed product. These and other defects in products arereduced when the differences between Vicat softening temperatures andspecific gravities of highly neutralized acid polymers are controlled.

However, the inventors have discovered that controlling only theseparameters may not ensure that a quality product, such as a golf ball,will result. For example, a manufacturer may seek to introduce anadditive. As the skilled practitioner recognizes, many such additivescompositions, such as brighteners, colors, and fillers, typically areadded to polymer products. However, many of these additives do not blendeasily with highly neutralized acid polymers. Further, moisture adsorbedby the highly neutralized acid polymers complicates processing.

The inventors have discovered that additives can be effectivelyintroduced into highly neutralized acid polymer, including blends ofhighly neutralized acid polymers, by incorporating a masterbatchcontaining the additives. The masterbatch comprises an ionomeric polymerthat is compatible with both the additives and the highly neutralizedacid polymers. Further, ionomers not only do not adsorb as much moistureas highly neutralized acid polymers, but also dry more easily thanhighly neutralized acid polymers.

The inventors also have discovered that controlling the Vicat softeningtemperatures and the specific gravities of the highly neutralized acidpolymers and the ionomer resin, and incorporating additives as part ofan ionomer-based masterbatch, not only yields excellent product qualitybut also simplifies processing.

The skilled practitioner recognizes that thermoplastic material can beprocessed in many ways, and typically is processed by injection moldingor compression molding. Injection molding is a process typically used inthe manufacture of golf balls. Successful injection molding requiresthat the composition being molded be flowable to fill a mold. Thus,formation of gas during injection will disrupt the process and maydamage the mold and other processing equipment, in addition to causingdefects in the product. Similarly, molding heterogeneous material maycause distribution problems in the mold and poor product quality due toproblems in controlling the mixing ratio.

In an embodiment of the invention, the Vicat softening temperatures ofthe polymeric components being blended are controlled so that thedifferences between the temperatures are within ranges that makeprocessing of the blend easy and result in high quality processedproducts. The specific gravities of the highly neutralized acid polymersalso are controlled. Also, a masterbatch comprising an ionomeric polymerand additives that are difficult to blend with highly neutralized acidpolymers is used to facilitate formation of the blend, to reduceintroduction of additional moisture into the product, and to make iteasier to remove moisture that is present.

For convenience, embodiments of the invention will be described withdetail as they relate to blends having 2 highly neutralized acid polymercomponents in the manufacture of golf balls. However, the inventionrelates to ternary, quaternary, and higher order highly neutralized acidpolymer blends and any product comprising highly neutralized acidpolymers. With the description provided herein, the skilled practitionerwill be able to apply the subject matter of the invention to blends ofany number of highly neutralized acid polymer components and themanufacture of products therewith.

The drawing figures illustrate selected golf ball constructions. FIG. 1shows a golf ball 100 in accordance with a first embodiment of thepresent disclosure. Golf ball 100 is a two-piece golf ball.Specifically, golf ball 100 includes cover layer 110 substantiallysurrounding core layer 120. In golf ball 100, core layer 120 may be madeof a blend of highly neutralized acid polymers.

FIG. 2 shows a golf ball 200 in accordance with a second embodiment ofthe present disclosure. Golf ball 200 includes a core layer 230, aninner cover layer 220 substantially surrounding core layer 230, and anouter cover layer 210 substantially surrounding inner cover layer 220.In some embodiments, both inner cover layer 220 and core layer 230 maycomprise the blended highly neutralized acid polymers described herein.

FIG. 3 shows a golf ball 300 in accordance with a third embodiment ofthe present disclosure. Golf ball 300 includes an inner core layer 330,an outer core layer 320 substantially surrounding inner core layer 330,and a cover layer 310 substantially surrounding outer core layer 320. Insome embodiments, inner core layer 330 and outer core layer 320 maycomprise blended highly neutralized acid polymers.

FIG. 4 shows a golf ball 400 in accordance with a fourth embodiment ofthe present disclosure. Golf ball 400 includes an inner core layer 440,an outer core layer 430 substantially surrounding inner core layer 440,an inner cover layer 420 substantially surrounding outer core layer 430,and an outer cover layer 410 substantially surrounding inner cover layer420. In some embodiments, any or all of inner cover layer 420, outercore layer 430, and inner core layer 440 can comprise blended highlyneutralized acid polymers.

In some embodiments, a cover layer comprises an inner cover layer 420essentially enclosing an outer core layer 420 and an outer cover layer410 essentially enclosing the inner cover layer.

Thus, each of these types of golf balls can be made in accordance withthe method disclosed herein. Also, golf balls with additional layers,such as 5 or more layers, can be made in accordance with the methoddisclosed herein. Except as otherwise discussed herein below, any golfball discussed herein may generally be any type of golf ball known inthe art. Namely, unless the present disclosure indicates to thecontrary, a golf ball may generally be of any constructionconventionally used for golf balls, such as a regulation ornon-regulation construction. Regulation golf balls are golf balls whichmeet the Rules of Golf as approved by the United States Golf Association(USGA). Golf balls discussed herein may also be made of any of thevarious materials known to be used in golf ball manufacturing, except asotherwise noted.

Furthermore, it is understood that any feature disclosed herein(including but not limited to various embodiments shown in the FIGS. andvarious chemical formulas or mixtures) may be combined with any otherfeatures disclosed here, as may be desired.

The skilled practitioner recognizes that additives often are added to agolf ball layer to modify the properties and characteristics of thatlayer. In particular, fillers often are used to increase the specificgravity or hardness of a layer. Fillers can be organic compounds, buttypically are inorganic compounds. Typical inorganic fillers includemetals, particularly in powder form, and metal oxides, sulfates,carbonates, and other forms. However, these inorganic fillers typicallyare difficult to blend with highly neutralized acid polymers. Thus, thedifficulty in forming blended highly neutralized acid polymers, combinedwith the difficulty in incorporating some additives, makes themanufacture of products, such as golf balls, a challenging process.

Further, highly neutralized acid polymers are hygroscopic. Moistureadsorbed by the highly neutralized acid polymers forms voids duringprocessing, for example, during injection molding or compression moldingto form a golf ball layer.

One approach to ameliorating the difficulty of incorporating fillers,for example, into highly neutralized acid polymers is to form amasterbatch. The skilled practitioner recognizes that masterbatchingherein would be expected to involve formation of a compositioncomprising a high concentration of additive in a small portion of highlyneutralized acid polymer. The masterbatch then would be blended into theproduct.

Masterbatching requires heating the highly neutralized acid polymer,blending the components, cooling, and comminuting the product. Themasterbatch material must be comminuted for further processing, often ina granulator after an extruder. However, the result of comminutiontypically is unsatisfactory. Although air-cooled granulators areavailable, they are not favored in the art, so a water-cooled granulatortypically is used. The highly neutralized acid polymers thus adsorbwater, which water is not easily removed before further processing.Moisture in the resin during injection will form voids in the productand the escaping vapor may damage equipment. Thus, masterbatching withhighly neutralized acid polymer is not a suitable alternative.

However, the inventors have discovered that a masterbatch of additivesin an ionomer resin provides a suitably easy and cost-effective way ofproducing these desirable products. Because ionomer resin does notadsorb moisture as highly neutralized acid polymer does, water-cooledgranulation can be used, with any moisture adsorbed easily removedbefore further processing.

In accordance with the invention, a first highly neutralized acidpolymer has a first Vicat softening temperature and a first specificgravity, a second highly neutralized acid polymer has a second Vicatsoftening temperature and a second specific gravity, and an ionomerresin has a third Vicat softening temperature and a third specificgravity. The inventors have discovered that blending of these two highlyneutralized acid polymers and the ionomer resin is facilitated if thedifferences among the first, second, and third Vicat softeningtemperatures are controlled within predetermined values, and typicallyare minimized. Thus, in an embodiment of the invention, the absolutevalues of the differences among Vicat softening temperatures of highlyneutralized acid polymers and ionomer resin to be blended are limited toabout 15° C. or less, typically about 10° C. or less, and more typicallyabout 8° C. or less. In other embodiments, the absolute values of thedifferences among the first Vicat softening temperature, the secondVicat softening temperature, and the third Vicat softening temperatureare about 5° C. or less, more typically about 2° C. or less, and evenmore typically about 1° C. or less.

In another aspect, the absolute values of the differences among thespecific gravities of the highly neutralized acid polymers and theionomer resin to be blended are controlled within predetermined values,and typically are minimized. In an embodiment, the absolute value of thedifference in specific gravities is limited to no more than about 0.015,typically no more than about 0.010, and more typically no more thanabout 0.005.

In a more typical embodiment, both the differences in Vicat softeningtemperatures and the differences in specific gravities are controlled.In embodiments, the differences can be individually limited to any ofthe ranges associated with that difference. Thus, the absolute values ofthe differences in Vicat softening temperatures are limited to about 15°C. or less, and the absolute values of the differences in specificgravities is limited to no more than about 0.015, typically no more thanabout 0.010, and more typically no more than about 0.005. Similarly, theabsolute values of the differences in Vicat softening temperature arelimited to about 10° C. or less, typically about 8° C. or less, moretypically is about 5° C. or less, still more typically about 2° C. orless, and even more typically about 1° C. or less, while the absolutevalues of the differences in specific gravities are limited to no morethan about 0.015, typically no more than about 0.010, and more typicallyno more than about 0.005.

Products comprising blends of highly neutralized acid polymerscontaining additives can be made with fewer defects in accordance withthe invention by injection molding, compression molding, or processingthe blend in accordance with any suitable manner for processingthermoplastic materials, by controlling the Vicat softening temperaturesand specific gravities, as described herein, and by introducing theadditives as part of an ionomer-based masterbatch. In particular, golfballs often are made, at least in part, by injection molding ofthermoplastic materials. Thus, a method of making golf balls can benefitfrom the method of controlling the Vicat softening temperatures andspecific gravities of the materials to be blended, and by introducingadditives as part of an ionomer-based masterbatch.

Thus, an embodiment of the invention is directed to a method ofmanufacturing a golf ball including a blend of highly neutralized acidpolymers and an ionomer resin by controlling the differences among Vicatsoftening temperatures of the highly neutralized acid polymers and theionomer resin to be blended, controlling the differences among thespecific gravities of the highly neutralized acid polymers and theionomer resin, introducing additives as part of an ionomer-basedmasterbatch, and processing the blended material to form at least a partof a golf ball.

In an embodiment, highly neutralized acid polymers and ionomer resinoften used in a blend of highly neutralized acid polymers used in themanufacture of golf balls have a Vicat softening temperature of betweenabout 30° C. and about 70° C., typically between about 40° C. and about65° C., and more typically between about 48° C. and about 65° C.

Highly neutralized acid polymers are copolymers or terpolymers with afatty acid salt. In embodiments of the invention, the ionomer resin usedto form the ionomer-based masterbatch is different from the copolymer orterpolymer present in any of the highly neutralized acid polymersforming the blend. Ionomer resins can be distinguished from highlyneutralized acid polymers by both structural differences and differencesin properties and characteristics. Structurally, ionomer resins areco-polymers devoid of fatty acid salt, whereas highly neutralized acidpolymers are co-polymers and terpolymers with a fatty acid salt. Whereassalts, hydroxides, carbonates, and other metal-containing compounds areused to provide some neutralizing ions in both ionomer resins and highlyneutralized acid polymers, fatty acid salts also are used in highlyneutralized acid polymers. Thus, the structures of an ionomer resin andof a highly neutralized acid polymer are distinct. The properties andcharacteristics of these compounds also are distinct. Ionomer resin isnot hygroscopic, but highly neutralized acid polymer is hygroscopic,typically because of the presence of the fatty acid salt. With theinformation and guidance provided herein, the skilled practitioner willbe able to identify ionomer resins and highly neutralized acid polymers.

As described herein, the specific gravities of the highly neutralizedacid polymers and the ionomer resin are controlled in embodiments of theinvention. In some embodiments of the invention, the ionomer-basedmasterbatch comprises filler, typically densifier, as an additive.Typically, therefore, in embodiments of the invention, the specificgravity of the inorganic filler is greater than the specific gravity ofany polymer (i.e., the highly neutralized acid polymers and the ionomerresin). In other embodiments, the specific gravity of the inorganicfiller is greater than the sum of the specific gravities of thepolymers.

Typically, embodiments are directed to golf balls having core layerscomprising blended highly neutralized acid polymers. More typically, theinner core layer of a golf ball comprises blended highly neutralizedacid polymers. In particular, the core layer, or inner core layer, ismade by injection molding. For convenience, embodiments of the inventionwill be described with particularity herein as they relate tomanufacturing the core layer or the inner core layer of a 3-piece or-layer golf ball or a 4-piece golf ball. However, with the informationand guidance provided herein, the skilled practitioner will be able todesign balls having more or different layers.

An embodiment is directed to a 3-piece golf ball having a core layer 230or an inner core layer 330, an inner cover layer 220 or an outer corelayer 320 substantially enclosing the respective inner layer, and outercover layer 210 or cover layer 310 substantially enclosing theirrespective inner layers.

Another embodiment is directed to a four-piece golf ball comprising aninner core layer 440; an outer core layer 430 substantially enclosingthe inner core layer; an intermediate or inner cover layer 420substantially enclosing the outer core layer, and an outer cover layer410 substantially enclosing the inner cover layer.

Typically, in these 3- and 4-piece ball constructions that areembodiments of the invention, the core layer or inner core layercomprises a blend comprising a first highly neutralized acid polymerhaving a first Vicat softening temperature of from about 48° C. to about65° C., a second highly neutralized acid polymer having a second Vicatsoftening temperature of from about 48° C. to about 65° C., and anionomer-based masterbatch comprising additives and an ionomer resinhaving a third Vicat softening temperature of from about 48° C. to about65° C., and the absolute values of the differences among the first,second, and third Vicat softening temperatures and the ionomer resin arecontrolled to no more than about 15° C.

In another typical embodiment, the inner core layer comprises a blendcomprising a first highly neutralized acid polymer having a firstspecific gravity and a first Vicat softening temperature, a secondhighly neutralized acid polymer having a second specific gravity and asecond Vicat softening temperature, and an ionomer-based masterbatchcomprising additives and an ionomer resin having a third Vicat softeningtemperature and a third specific gravity, and the absolute values of thedifferences among the first, second, and third Vicat softeningtemperatures and the absolute values of the differences among the first,second, and third specific gravities are controlled within predeterminedvalues, thus facilitating forming a thermoplastic inner core layercomprising a blend of highly neutralized acid polymers. More typically,the absolute values of the differences among Vicat softeningtemperatures is no more than about 15° C., and the absolute values ofthe differences among specific gravities is no more than about 0.015.Even more typically, for the first and second highly neutralized acidpolymers, the absolute values of the difference between the first Vicatsoftening temperature and second Vicat softening temperature is lessthan about 5° C.

Often, an inner core layer of an embodiment of the invention has aspecific gravity between about 0.85 to about 1.1, typically betweenabout 0.9 and about 1.1. In embodiments, the specific gravity isadjusted to adjust the moment of inertia (MOI) to affect the spin rateof the ball. Lowering the specific gravity of the inner core layer to avalue less than about the specific gravities of the outer layers willincrease the MOI and reduce the spin rate. Alternatively, increasing thespecific gravity of the inner core layer decreases the MOI and increasesthe spin rate. With the information and guidance provided herein, theskilled practitioner can select a specific gravity of the blend toprovide a desired MOI and can control the specific gravities of thehighly neutralized acid polymers in the blend to form a homogeneousblend that forms a defect-free product.

In embodiments, a thick thermoset outer core layer often is used toprotect the thermoplastic inner core layer. The thickness of the outercore layer typically is between about 5 mm and about 9 mm. Also, to havegood flight performance, the outer core layer, with the inner core layertherein, has a high coefficient of restitution (COR). Typically, the CORis at least about 0.8. To have a good spin rate of mid or short ironshots, the outer cover layer has a low flexural modulus, typically lessthan about 1,000 psi. Embodiments of the invention also include 4-piecegolf balls in which the inner cover layer has a high Shore D hardness,typically at least about 60, to reduce the spin rate of driver shots. Inparticular, to have a good moment of inertia, the inner cover layer hasa greater specific gravity than the thermoset outer core layer.Embodiments of the invention also include a cross-linked thermoplastichaving a flexural modulus of less than about 1,000 psi to provide goodspin rate for mid- and short-iron shots.

As used herein, unless otherwise noted, Vicat softening temperature,compression deformation, hardness, COR, and flexural modulus, aremeasured as follows:

Vicat softening temperature: Measured in accordance with ASTM D-1525.

Compression deformation: The compression deformation herein indicatesthe deformation amount of a golf ball, or part thereof, under a force.Specifically, when the force is increased to 130 kg from 10 kg, thedeformation amount of the golf ball or part thereof under a force of 130kg, less the deformation amount of the golf ball or part thereof under aforce of 10 kg, is the compression deformation value. For example, agolf ball that deforms 0.5 mm under a 10 kg force and 5.0 mm under a 130kg force has a compression deformation of 4.5 mm.

Hardness: Hardness of golf ball layer is measured generally inaccordance with ASTM D-2240, but is measured on the land area of acurved surface of a molded golf ball.

Method of measuring COR: A golf ball is fired by an air cannon at asteel plate positioned about 1.2 meters away from the air cannon at aninitial velocity of 40 m/sec. A speed monitoring device is located overa distance of 0.6 to 0.9 meters from the cannon. After striking theplate, the golf ball rebounds through the speed-monitoring device. Thereturn velocity divided by the initial velocity is the COR.

Flexural modulus: Measured in accordance with ASTM D-790.

In embodiments in which the inner core layer 440 has a high resilience,the golf ball 400 will have a good flight performance. In embodiments ofthe invention, therefore, outer core layer 430 with inner core layer 440in it typically has a COR value from at least about 0.80, more typicallyat least about 0.81, and more typically at least about 0.82. In someembodiments, inner core layer 440 has a first coefficient ofrestitution, golf ball 400 has a second coefficient of restitution, andthe first coefficient of restitution is greater than the secondcoefficient of restitution. Typically, the first coefficient ofrestitution is at least about 0.01 greater than the second coefficientof restitution.

Inner core layer 440 typically is made by an injection molding process,although a compression molding process may also be used. During aninjection molding process, the temperature of the injection machinetypically is set in a range of about 190° C. to about 220° C.

However, before the injection molding process, first and second highlyneutralized acid polymers, a blend thereof, the ionomer resin, and theionomer-based masterbatch, should be kept in a moisture-resistantpackaging or should be treated with a dry gas, typically air, to reducethe moisture level. Moisture in the compounds will cause voids in theproduct. Drying conditions for highly neutralized acid polymerstypically require 2 to 24 hours of dry air flow at a temperature belowabout 50° C. Because the ionomer resin does not adsorb as much moistureas does highly neutralized acid polymer, drying conditions for ionomerresins are less severe, and drying may not be necessary if the moisturecontent of the ionomer resin in the ionomer-based masterbatch is not toohigh. Moisture levels greater than 2,000 ppm in the highly neutralizedacid polymer may make it necessary to employ vacuum as well as heat toremove moisture therefrom. The moisture level should be no more thanabout 1,000 ppm for production of products free from defects caused bymoisture.

After drying, if necessary, the highly neutralized acid polymers and theionomer-based masterbatch may be dry-blended or be compounded in anextruder, for example, preparatory to injection molding to form aproduct, herein typically the inner core layer of a golf ball. Althoughcompounding produces a more intimate mixture and helps ensurehomogeneity of product, dry blending is sufficient. The blend then isfurther processed in, for example, an injection molding process, to forma product, such as a layer of a golf ball.

Any ratio of components can be blended. In one embodiment, theconcentration range of the first highly neutralized acid polymer isbetween about 10 wt percent to about 70 wt percent, based on the weightof the blended product; the second highly neutralized acid polymer ispresent at about 10 wt percent to about 70 wt percent, based on theweight of the blended product; and the concentration of ionomer-basedmasterbatch is between about 1 wt percent and about 30 wt percent, basedon the weight of the blended product. In another embodiment, the highlyneutralized acid polymers are present in an independently selectedconcentration of between about 20 wt percent to about 60 wt percenteach, and the concentration of the ionomer-based masterbatch is betweenabout 10 and about 25 wt percent.

In embodiments of the invention, suitable highly neutralized acidpolymers include, but are not limited to, HPF resins such as HPF1000,HPF2000, HPF AD1024, HPF AD1027, HPF AD1030, HPF AD1035, HPF AD1040, allproduced by E. I. Dupont de Nemours and Company. In embodiments, corelayer 440 comprises a blend of highly neutralized acid polymers andoptionally additives, fillers, and/or melt flow modifiers. The acidpolymer typically is neutralized to 80 percent or higher, including upto 100 percent, with a suitable cation source, such as magnesium,sodium, zinc, or potassium. The cation source of first and second highlyneutralized acid polymers may be the same or different.

The masterbatch comprises an ionomer resin and an inorganic filler.Suitable ionomer resin in embodiments of the invention has a Vicatsoftening temperature of from about 48° C. to 65° C., such as Surlyn®6910, Surlyn® 9910, Surlyn® 8920, Surlyn® 7940, Surlyn® 8940, Surlyn®8941, Surlyn® 6120, Surlyn® 8140, Surlyn® 8150, Surlyn® 9150, Surlyn®8120, Surlyn® 9020, Surlyn® 6320, Surlyn® 9320, and Surlyn® 9320W, orIotek® (products available from ExxonMobil Chemical Company) of similarVicat softening temperature. Suitable inorganic fillers include, but arenot limited to, zinc oxide, titanium dioxide, tin oxide, calcium oxide,magnesium oxide, barium sulfate, zinc sulfate, zinc carbonate, bariumcarbonate, and metal powder such as tungsten powder, and molybdenumpowder. Other suitable inorganic fillers include mica, talc, clay,silica, lead silicate, and the like.

In embodiments of the invention, the inorganic filler has a specificgravity greater than the specific gravities of the first and secondhighly neutralized acid polymers and of the ionomer resin. Typically,the specific gravity of the filler is greater than the sum of the first,second, and third specific gravities. It is typical that the inorganicfiller of the masterbatch has a density of more than 3 g/cm³ to impart agreater specific gravity in the layer.

Typically, the weight fraction of the inorganic filler in themasterbatch is greater than the fraction of the ionomer resin. Inembodiments of the invention, the weight fraction of the ionomer resincan be from about 10 wt percent to about 45 wt percent of theionomer-based masterbatch. Accordingly, the weight fraction of theinorganic filler can be from about 90 wt percent to about 55 wt percentof the ionomer-based masterbatch.

To add color of inner core layer 440, the masterbatch may optionallyinclude a color agent. Typically, color agent comprises less than about1 wt percent of the ionomer-based masterbatch.

In addition to filler, other additives may be incorporated into theblend. Suitable additives and fillers include, for example, blowing andfoaming agents, optical brighteners, coloring agents, fluorescentagents, whitening agents, UV absorbers, light stabilizers, defoamingagents, processing aids, mica, talc, nanofillers, antioxidants,stabilizers, softening agents, fragrance components, plasticizers,impact modifiers, acid copolymer wax, surfactants, and regrind, i.e.,core material that is ground and recycled. These other additives can beadded as part of the ionomer-based masterbatch or, more typically, areincorporated directly into the highly neutralized acid polymer.

Suitable melt flow modifiers include, for example, fatty acids and saltsthereof, polyamides, polyesters, polyacrylates, polyurethanes,polyethers, polyureas, polyhydric alcohols, and combinations thereof.

Each of the compounds discussed herein for any particular embodiment maybe mixed and matched with any other specific embodiment of anothercompound according to the description herein. Furthermore, any compoundmay generally be used in combination with other compounds of the sametype, such that any list herein includes mixtures thereof, unlessotherwise specified.

In embodiments of the invention, the diameter of inner core layer 440may be in a range of from about 21 mm to about 28 mm, or from about 24mm to about 28 mm.

Inner core layer 440 typically has a compression deformation value in arange of from about 3 mm to about 5 mm. In some embodiments, inner corelayer 440 has a compression deformation value in a range of from about 3mm to about 4.5 mm. Further, inner core layer 440 has a surface Shore Dhardness of from 45 to 55 at any single point on a cross-sectionobtained by cutting inner core layer 440 in half, and has a Shore Dcross-sectional hardness difference between any two points on thecross-section of within ±6. This hardness condition ensures that thegolf ball will exhibit stable performance. In some embodiments, thehardness difference between any two points on the cross-section iswithin ±3.

Outer core layer 320 or 430 typically is formed of thermoset materials,typically by crosslinking a polybutadiene rubber composition. When otherrubber is used in combination with a polybutadiene, it is typical thatpolybutadiene is included as a principal component. Specifically, aproportion of polybutadiene in the entire base rubber typically is equalto or greater than about 50 percent by weight, and more typically isequal to or greater than about 80 percent by weight. A polybutadienehaving a proportion of cis-1,4 bonds of equal to or greater than about60 mol percent, and further, equal to or greater than about 80 molpercent, is most typical.

In some embodiments, cis-1,4-polybutadiene may be used as the baserubber and mixed with other ingredients. In some embodiments, the amountof cis-1,4-polybutadiene may be at least about 50 parts by weight, basedon 100 parts by weight of the rubber compound.

Various additives may be added to the base rubber to form a compound.The additives may include a cross-linking agent and a filler. In someembodiments, the cross-linking agent may be zinc diacrylate, magnesiumacrylate, zinc methacrylate, or magnesium methacrylate. In someembodiments, zinc diacrylate may provide advantageous resilienceproperties.

The filler may be used to increase the specific gravity of the rubbercompound. The filler may include zinc oxide, barium sulfate, calciumcarbonate, or magnesium carbonate. In some embodiments, zinc oxide maybe selected for its advantageous properties. Metal powder, such astungsten, may alternatively be used as a filler to achieve a desiredspecific gravity. In some embodiments, the specific gravity of outercore layer 320 or 430 may be from about 1.05 to about 1.45. In someembodiments, the specific gravity of outer core layer 320 or 430 may befrom about 1.05 to about 1.35.

In some embodiments, a polybutadiene synthesized using a rare earthelement catalyst may be used. In some embodiments, rare earth elementcatalysis of the polybutadiene reaction is typical. Excellent resilienceperformance of a golf ball may be achieved by using this polybutadiene.Examples of rare earth element catalysts include lanthanum series rareearth element compounds. Other catalysts may include an organoaluminumcompound, an alumoxane, and halogen containing compounds. A lanthanumseries rare earth element compound is typical. Polybutadiene obtained byusing lanthanum series rare earth-based catalysts usually employs acombination of lanthanum series rare earth (atomic number of 57 to 71)compounds, but particularly typical is a neodymium compound.

In some embodiments, the polybutadiene rubber composition may compriseat least from about 0.5 parts by weight to about 5 parts by weight of ahalogenated organosulfur compound. In some embodiments, thepolybutadiene rubber composition may comprise at least from about 1 partby weight to about 4 parts by weight of a halogenated organosulfurcompound. The halogenated organosulfur compound is selected from thegroup consisting of pentachlorothiophenol; 2-chlorothiophenol;3-chlorothiophenol; 4-chlorothiophenol; 2,3-chlorothiophenol;2,4-chlorothiophenol; 3,4-chlorothiophenol; 3,5-chlorothiophenol;2,3,4-chlorothiophenol; 3,4,5-chlorothiophenol;2,3,4,5-tetrachlorothiophenol; 2,3,5,6-tetrachlorothiophenol;pentafluorothiophenol; 2-fluorothiophenol; 3-fluorothiophenol;4-fluorothiophenol; 2,3-fluorothiophenol; 2,4-fluorothiophenol;3,4-fluorothiophenol; 3,5-fluorothiophenol; 2,3,4-fluorothiophenol;3,4,5-fluorothiophenol; 2,3,4,5-tetrafluorothiophenol;2,3,5,6-tetrafluorothiophenol; 4-chlorotetrafluorothiophenol;pentaiodothiophenol; 2-iodothiophenol; 3-iodothiophenol;4-iodothiophenol; 2,3-iodothiophenol; 2,4-iodothiophenol;3,4-iodothiophenol; 3,5-iodothiophenol; 2,3,4-iodothiophenol;3,4,5-iodothiophenol; 2,3,4,5-tetraiodothiophenol;2,3,5,6-tetraiodothiophenol; pentabromothiophenol; 2-bromothiophenol;3-bromothiophenol; 4-bromothiophenol; 2,3-bromothiophenol;2,4-bromothiophenol; 3,4-bromothiophenol; 3,5-bromothiophenol;2,3,4-bromothiophenol; 3,4,5-bromothiophenol;2,3,4,5-tetrabromothiophenol; 2,3,5,6-tetrabromothiophenol; and theirzinc salts and other metal salts thereof, and mixtures thereof.

Outer core layer 320 or 430 typically is made by compression molding.Suitable vulcanization conditions include a vulcanization temperature ofbetween about 130° C. and about 190° C. and a vulcanization time ofbetween about 5 and about 20 minutes. To obtain the desired rubbercrosslinked body for use as a layer, particularly outer core layer 320or 430, of the golf ball described herein, the vulcanization temperatureis preferably at least about 140° C.

Typically, outer core layer 430 has a surface Shore D hardness of from50 to 60, and the surface hardness of outer core layer 430 is higherthan the surface hardness of inner core layer 440.

When outer core layer 430 is produced by vulcanizing and curing therubber composition in the above-described way, advantageous use may bemade of a method in which the vulcanization step is divided into twostages: first, the outer core layer material is placed in an outer corelayer-forming mold and subjected to an initial vulcanization so as toproduce a pair of semi-vulcanized hemispherical cups, following which aprefabricated inner core layer is placed in one of the hemisphericalcups and is covered by the other hemispherical cup, in which statecomplete vulcanization is carried out.

The surface of inner core layer 440 placed in the hemispherical cups maybe roughened before the placement to increase adhesion between innercore layer 440 and outer core layer 430. In some embodiments, the innercore layer surface may be pre-coated with an adhesive or pre-treatedwith chemical(s) before placing inner core layer 440 in thehemispherical cups to enhance the durability of the golf ball and enablea high rebound.

Outer cover layer 410 of golf ball 400 typically has a thickness of fromabout 0.5 mm to about 2 mm. In some embodiments, outer cover layer 310of the present disclosure has a thickness of from about 0.8 mm to about2 mm. In some embodiments, outer cover layer 410 has a thickness of fromabout 1 mm to about 1.7 mm.

Typically, inner cover layer 420 may comprise a thermoplastic material.The thermoplastic material of an inner cover layer may comprise at leastone of an ionomer resin, a highly neutralized acid polymer, a polyamideresin, a polyurethane resin, a polyester resin, and a combinationthereof.

Some embodiments are directed to a 4-piece golf ball. In theseembodiments, inner cover layer 420 may comprise the same crosslinkedthermoplastic polyurethane as an outer cover layer 410 (discussedbelow). In some embodiments, the inner cover layer comprises anuncrosslinked thermoplastic polyurethane different from an outer coverlayer, while in some embodiments, the inner cover layer comprises anentirely different type material from the outer cover layer. In someembodiments, inner cover layer 420 comprises the same material as outercover layer 410. In some embodiments, the inner cover (intermediate)layer has a thickness less than the thickness of the outer cover layer.

In some embodiments, outer cover layer 410 comprises a cross-linked TPUelastomer including cross-links formed from allyl side chain moieties.The cross-linked TPU elastomer is polyurethane that is the reactionproduct of an organic isocyanate with a mixture of the followingreactants:

(a) a diol having 2 primary hydroxyl groups and at least 1 pendantunsaturation having the following formula:

in which R¹ may be any suitable substituted or unsubstituted alkyl,substituted or unsubstituted aryl, substituted or unsubstitutedalkyl-aryl group, substituted or unsubstituted ether group, substitutedor unsubstituted ester group, any combination of the above groups, or H,and may optionally include an unsaturated bond in any main chain or sidechain of any group; R² may be any suitable substituted or unsubstitutedalkyl, substituted or unsubstituted aryl, substituted or unsubstitutedalkyl-aryl group, substituted or unsubstituted ether group, substitutedor unsubstituted ester group, any combination of the above groups, andR² may include an allyl group; and x and y are integers independentlyhaving any value from 1 to 10;

(b) a chain extender having at least two reaction sites with isocyanatesand having a molecular weight of less than about 450;

(c) a long chain polyol having a molecular weight of between about 500and about 4,000; and

(d) a sufficient amount of free radical initiator, so as to be capableof generating free radicals that induce crosslinking structures in thehard segments by free radical initiation.

The chemical groups in formula (1) may have their conventionaldefinitions as is generally known in the art of chemistry. Specifically,an unsubstituted alkyl group includes any chemical group comprising onlycarbon and hydrogen linked by single bonds. A substituted alkyl groupmay include atoms other than carbon and hydrogen in a side chainportion, such as a halogen group, an inorganic group, or otherwell-known functional groups. In some embodiments, a substituted orunsubstituted alkyl group may include from 1 to about 100 carbon atomsin the alkyl chain. In other embodiments, a substituted or unsubstitutedalkyl group may have from 1 to 10 carbon atoms in the alkyl chain. Analkyl group, or any portion thereof, or alkyl substituent, may be astraight chain or branched.

As is further known in the art of chemistry, an aryl group is defined asany group that includes an aromatic benzene ring. Furthermore, analkyl-aryl group includes at least one aromatic benzene ring in additionto at least one alkyl carbon. An ether group includes at least oneoxygen atom bonded to two carbon atoms. An ester group includes at leastone carbon atom that is double bonded to a first oxygen atom and singlebonded to a second oxygen atom, which also is bonded to a second carbonatom.

In specific embodiments, the unsaturated diol may include an allyl ethergroup as the side chain. For example, the unsaturated diol may berepresented by formula (2) shown below:

in which R is a substituted or unsubstituted alkyl group, and x and yare integers independently having values of 1 to 4. In particularembodiments, x and y may both have values of 1, 2, 3 or 4. In otherembodiments, x and y may each have different values from 1 to 4.

Typically, the diol having pendant unsaturation is trimethylolpropanemonoallyl ether (“TMPME”). Reference is made to applicants' co-pendingU.S. application Ser. No. 12/827,360, filed Jun. 30, 2010, the entiretyof which is hereby incorporated by reference.

The organic isocyanate may include any of the known aromatic, aliphatic,and cycloaliphatic di- or polyisocyanates. Examples of suitableisocyanates include: 2,2′-, 2,4′- (and particularly) 4,4-diphenylmethanediisocyanate, and isomeric mixtures thereof (“MDI”); polyphenylenepolymethylene polyisocyanates (poly-MDI, PMDI); 2,4- and 2,6-toluenediisocyanates, and isomeric mixtures thereof such as an 80:20 mixture ofthe 2,4- and 2,6-isomers (“TDI”); isophorone diisocyanate;1,4-diisocyanatobutane; 1,5-diisocyanatopentane; 1,6-diisocyanatohexane;1,4-cyclohexane diisocyanate; cycloaliphatic analogs of PMDI; and thelike.

Suitable optional second chain extenders may include the common diols,such as ethylene glycol, diethylene glycol, triethylene glycol,propylene glycol, dipropylene glycol, tripropylene glycol,1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol,neopentyl glycol, dihydroxyethoxy hydroquinone,1,4-cyclo-hexanedimethanol, 1,4-dihydroxycyclohexane, and the like.Minor amounts of crosslinking agents such as glycerine,trimethylolpropane, diethanolamine, and triethanolamine may be used inconjunction with the diol chain extenders.

In addition to the common diol chain extenders, diamines and aminoalcohols may also be used as the optional second chain extender.Examples of suitable diamines include aliphatic, cycloaliphatic oraromatic diamines. In particular, a diamine chain extender may beethylene diamine, hexamethylene diamine, 1,4-cyclohexyene diamine,benzidine, toluene diamine, diaminodiphenyl methane, the isomers ofphenylene diamine or hydrazine. Aromatic amines may also be used, suchas MOCA (4,4′-methylene-bis-o-chloroaniline), M-CDEA(4,4′-methylenebis(3-chloro-2-6-diethyl-aniline)). Examples of suitableamino alcohols are ethanol amine, N-methylethanolamine,N-butylethanolamine, N-oleylethanolamine, N-cyclohexylisopropanolamine,and the like. Mixtures of various types of chain extenders may also beused to form the crosslinked thermoplastic polyurethane.

The long chain polyol (“the polyol”) may generally be a polyester polyolor a polyether polyol. Accordingly, the crosslinked thermoplasticpolyurethane may be either general type of polyurethane: a polyetherbased polyurethane elastomer or a polyester based polyurethaneelastomer, or mixtures thereof.

The long chain polyol may be a polyhydroxy compound having a molecularweight between 500 and 4,000. Suitable long chain polyols may generallyinclude linear polyesters, polyethers, polycarbonates, polylactones(e.g., ε-caprolactone), and mixtures thereof. In addition to polyolshaving hydroxyl terminal groups, the polyol may include carboxyl, aminoor mercapto terminal groups.

Polyester polyols are produced by the reaction of dicarboxylic acids anddiols or esterifiable derivatives thereof. Examples of suitabledicarboxylic acids include succinic acid, glutaric acid, adipic acid,suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid,maleic acid, fumaric acid, phthalic acid, isophthalic acid, andterephthalic acid. Examples of suitable diols include ethanediol,diethylene glycol, 1,2- and 1,3-propanediol, dipropylene glycol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol,glycerine and trimethylolpropanes, tripropylene glycol, tetraethyleneglycol, tetrapropylene glycol, tetramethylene glycol,1,4-cyclohexane-dimethanol, and the like. Both of the dicarboxylic acidsand diols can be used individually or in mixtures to make specificpolyesters in the practice applications.

Polyether polyols are prepared by the ring-opening additionpolymerization of an alkylene oxide with an initiator of a polyhydricalcohol. Examples of suitable polyether polyols are polypropylene glycol(PPG), polyethylene glycol (PEG), polytetramethylene ether glycol(PTMEG). Block copolymers such as combinations of polyoxypropylene andpolyoxyethylene glycols, poly-1,2-oxybutylene and polyoxyethyleneglycols, poly-1,4-tetramethylene and polyoxyethylene glycols are alsotypical in the present invention.

Polycarbonate polyols are made through a condensation reaction of diolswith phosgene, chloroformic acid ester, dialkyl carbonate or diallylcarbonate. Examples of diols in the suitable polycarbonate polyols ofthe crosslinked thermoplastic polyurethane elastomers are ethanediol,diethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol,neopentylglycol, and 1,5-pentanediol.

The crosslinked thermoplastic polyurethane elastomer may comprise asufficient amount of free radical initiator so as to be capable ofinducing crosslinking structures in the hard segments by free radicalinitiation. The free radical initiator may generate free radicalsthrough thermal cleavage or UV radiation. When the half-life of the freeradical initiator and its operation temperature are considered in themanufacturing process, the weight ratio of initiators to unsaturateddiols may be from 0.1:100 to 100:100. In particular embodiments, theweight ratio of free radical initiator to unsaturated diols may be about5:100.

A variety of known free radical initiators may be used as the radicalsource in order to make the present polyurethane elastomer having acrosslinking structure. Suitable radical initiators may includeperoxides, sulfurs, and sulfides, and peroxides may be particularlysuitable in some embodiments. The peroxides may be aliphatic peroxides,aromatic peroxides, or mixtures thereof. Peroxides such asdiacetylperoxide, di-tert-butylperoxide, dicumylperoxide,dibenzoylperoxide, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane,2,5-dimethyl-2,5-di(butylperoxy)-3-hexyne,2,5-bis-(t-butylperoxy)-2,5-dimethyl hexane,n-butyl-4,4-bis(t-butylperoxyl)valerate,1,4-bis-(t-butylperoxyisopropyl)-benzene, t-butyl peroxybenzoate,1,1-bis-(t-butylperoxy)-3,3,5 tri-methylcyclohexane, anddi(2,4-dichloro-benzoyl) peroxide may be used as the free radicalinitiator in some embodiments.

In some embodiments, inner cover layer 420 has a Shore D hardness asmeasured on the curved surface of at least about 60, higher than theShore D of outer cover layer 410, thus reducing spin rate on a drivershot. In some embodiments, outer cover layer 410 of golf ball 400 has aShore D hardness as measured on the curved surface from about 45 toabout 60.

To have a good spin performance for short iron shots, outer cover layer410 has a flexural modulus less than about 1,000 psi.

Other properties may be desirable for golf ball 300 or 400. In someembodiments, it may be desirable for golf ball 300 or 400 to have amoment of inertia between about 82 g-cm² and about 90 g-cm². Such amoment of inertia may produce a desirable distance and trajectory,particularly when golf ball 300 or 400 is struck with a driver or drivenagainst the wind.

Typically, golf ball 300 or 400 will have a compression deformation ofabout 2.2 mm to about 4 mm. In some embodiments, golf ball 300 or 400has compression deformation of about 2.5 mm to about 3.5 mm. In someembodiments, golf ball 300 or 400 has compression deformation of about2.5 mm to about 3 mm.

In some embodiments, the layers used to make golf ball 400 may have aspecified relationship in terms of their respective physical properties.For example, for a greater moment of inertia, outer core layer 430 has afourth specific gravity, and inner cover layer 420 has a fifth specificgravity, and the fifth specific gravity is greater than the fourthspecific gravity.

After the cover layer is made, golf ball 300 or 400 has a dimple patternwhich provides coverage of 70 percent or more. Golf ball 300 or 400 thenmay undergo various further processing steps such as buffing, primercoating, stamping, and top coating.

EXAMPLES

Golf balls in accordance with the present invention were fabricated asdescribed below, and voids (bubble defects) in the inner core layer werecompared to voids found in comparative examples.

For each golf ball, the masterbatch was selected from Table 1; innercore layer was made from a material selected from Table 2; the outercore layer was made from a material selected from Table 3; the innercover (intermediate) layer (if present) was made from a materialselected from Table 4; and the cover layer or outer cover layer was madefrom a material selected from Table 5-1 or Table 5-2. The amounts of thematerials listed in Tables 1, 2, 3, 4, 5-1, and 5-2 are shown in partsby weight (pbw) or percentages by weight.

TABLE 1 Masterbatch Materials A B Surlyn ® 8940 40 0 Barium sulfate 6060 HPF 2000 0 40

Surlyn® 8940 is a trade name of ionomeric resins by E. I. DuPont deNemours and Company. HPF 2000 is a trade name of a highly neutralizedacid polymer resin by E. I. DuPont de Nemours and Company. MasterbatchesA and B were made using a water-cooling granulating machine.

TABLE 2 Inner Core Layer Materials Resin: C D HPF 2000 68 68 HPF AD 103512 12 Masterbatch A 20 0 Masterbatch B 0 20

HPF 2000 and HPF AD 1035 are trade names of highly neutralized acidpolymer resins by E. I. DuPont de Nemours and Company.

TABLE 3 Outer Core Layer Materials Rubber compound: E F G TAIPOL ™BR0150 100 100 100 Zinc diacrylate 29 29 24 Zinc oxide 9 9 6 Bariumsulfate 11 9 39.5 Peroxide 1 1 1

TAIPOL™ BR0150 is the trade name of a rubber produced by TaiwanSynthetic Rubber Corp.

TABLE 4 Inner cover/Intermediate Layer Material Resin: H Neothane 6303D100

Neothane 6303D is the trade name of a thermoplastic polyurethaneproduced by Dongsung Highchem Co. LTD.

TABLE 5-1 Cover/Outer Cover Layer Materials I PTMEG (pbw) 100 BG (pbw)15 TMPME (weight % to total components)  10% DCP (weight % to totalcomponents) 0.5% MDI (pbw) 87.8 (NCO index) 1.01

TABLE 5-2 Cover/Outer Cover Layer Materials J Surlyn ® 8940 50 Surlyn ®9910 50

Surlyn® 9910 is trade name of ionomeric resin by E. I. DuPont de Nemoursand Company.

“PTMEG” is polytetramethylene ether glycol, having a number averagemolecular weight of 2,000, and is commercially available from Invista,under the trade name of Terathane® 2000. “BG” is 1,4-butanediol,commercially available from BASF and other suppliers. “TMPME” istrimethylolpropane monoallylether, commercially available from PerstorpSpecialty Chemicals AB. “DCP” is dicumyl peroxide, commerciallyavailable from LaPorte Chemicals Ltd. Finally, “MDI” is diphenylmethanediisocyanate, commercially available from Huntsman, under the trade nameof Suprasec® 1100.

Cover layer material I was formed by mixing PTMEG, BG, TMPME, DCP andMDI in the proportions shown. Specifically, these materials wereprepared by mixing the components in a high agitation stir for 1 minute,starting at a temperature of about 70° C., followed by a 10-hour postcuring process at a temperature of about 100° C. The post-curedpolyurethane elastomers then were ground into small chips. Cover layermaterial J was made by blending the two Surlyn® compounds.

Six golf balls were manufactured from the above materials. The identityand amount of each layer of each ball is shown in Table 6. Examples 1and 2 and comparative examples 4 and 5 were 4-piece golf balls, whereasexample 3 and comparative example 6 were 3-piece golf balls. Generally,the golf balls were manufactured using conventional compression moldingand injection molding processes known in the art of golf ballmanufacturing.

After the golf balls were finished, the golf balls were cut in half andthe void defects (air bubbles) in the inner core layer were identified.

TABLE 6 Golf Ball Testing Data Examples Comparative examples 1 2 3 4 5 6Inner Core Layer Material C C C D D D Diameter (mm) 24 21 28 24 21 28Shore D Hardness 53 53 53 53 53 53 Compression 3.2 3.5 3.0 3.2 3.5 3.0Deformation (mm) COR 0.83 0.83 0.83 0.83 0.83 0.83 Outer Core LayerMaterial E F G E F G Thickness (mm) 7.25 8.75 5.25 7.25 8.75 5.25 ShoreD Hardness 59 58 51 59 58 51 Inner Cover/- Intermediate Layer Material HH None H H None Thickness (mm) 1.0 1.0 X 1.0 1.0 X Shore D Hardness 6968 X 69 68 X Flexural Modulus(psi) 77,00.0 77,000 X 77,000 77,000 XOuter Cover/Cover layer Resin I I J I I J Thickness (mm) 1.1 1.1 1.7 1.11.1 1.7 Shore D Hardness 53 53 69 53 53 69 Flexural Modulus(psi) 550 55049,000 550 550 49,000 Inner core layer No No No Yes Yes Yes voids (airbubbles)

As shown in Table 6, voids did not form in the inner cores (Examples 1,2, and 3) comprising an ionomer resin masterbatch, whereas voids formedin the inner core layers comprising only highly neutralized acidpolymers masterbatch (Comparative examples 4, 5, and 6).

While various embodiments of the invention have been described, thedescription is intended to be exemplary, rather than limiting and itwill be apparent to those of ordinary skill in the art that many moreembodiments and implementations are possible that are within the scopeof the invention. Accordingly, the invention is not to be restrictedexcept in light of the attached claims and their equivalents. Also,various modifications and changes may be made within the scope of theattached claims.

What is claimed is:
 1. A golf ball comprising an inner core layercomprising a blend comprising a first highly neutralized acid polymerhaving a first Vicat softening temperature and a first specific gravity,a second highly neutralized acid polymer having a second Vicat softeningtemperature and a second specific gravity, and an ionomer-basedmasterbatch comprising an additive and an ionomer resin having a thirdVicat softening temperature, an outer core layer having a thicknessbetween about 5 mm and about 9 mm essentially enclosing the inner corelayer and comprising thermoset material, and a cover layer essentiallyenclosing the outer core layer, wherein the absolute values of thedifferences among the Vicat softening temperatures is no more than about15° C. and the absolute value of the difference between the specificgravities is no more than about 0.015; further comprising anintermediate layer situated between the outer core layer and the coverlayer; wherein the cover layer comprises a crosslinked thermoplasticpolyurethane elastomer including crosslinks formed from allyl groups,and the crosslinked thermoplastic polyurethane elastomer is a reactionproduct formed from reacting an organic isocyanate with a mixture of thefollowing reactants: (a) a diol having 2 primary hydroxyl groups and atleast 1 pendent unsaturation having the following formula:

in which R¹ is a substituted or unsubstituted alkyl group, substitutedor unsubstituted aryl group, substituted or unsubstituted alkyl-arylgroup, which may optionally include an ether or ester group, or anunsaturated bond in any main chain or side chain of any group, or is H;R² is a substituted or unsubstituted alkyl group, substituted orunsubstituted aryl group, or substituted or unsubstituted alkyl-arylgroup, which may optionally include an ether or ester group, and R²includes an allyl group; and x and y are integers independently havingany value from 1 to 10; (b) a chain extender having at least tworeaction sites with isocyanates and having a molecular weight of lessthan about 450; (c) a long chain polyol having a molecular weight ofbetween about 500 and about 4,000; and (d) a sufficient amount of freeradical initiator, so as to be capable of generating free radicals thatinduce crosslinking structures in the hard segments by free radicalinitiation.
 2. A golf ball according to claim 1, wherein the ionomerresin has a third specific gravity and the additive is a filler having aspecific gravity greater than the first, second, and third specificgravities.
 3. A golf ball according to claim 2, wherein the specificgravity of the filler is greater than the sum of the first, second, andthird specific gravities.
 4. A golf ball according to claim 3, whereinthe specific gravity of the filler is greater than about
 3. 5. A golfball according to claim 1, wherein the additive is a filler selectedfrom the group consisting of zinc oxide, titanium dioxide, tin oxide,calcium oxide, magnesium oxide, barium sulfate, zinc sulfate, zinccarbonate, barium carbonate, tungsten powder, and molybdenum powder, andblends thereof.
 6. A golf ball according to claim 1, wherein theionomer-based masterbatch comprises at least about 55 wt percentadditive.
 7. A golf ball according to claim 1, wherein the inner corelayer has a diameter of from 21 mm to 28 mm.
 8. A golf ball according toclaim 1, wherein the first Vicat softening temperature is between about48° C. and about 65° C., the second Vicat softening temperature isbetween about 48° C. and about 65° C., and the third Vicat softeningtemperature is between about 48° C. and about 65° C.
 9. A golf ballaccording to claim 1, wherein the absolute value of the differencesamong the Vicat softening temperatures is less than about 5° C.
 10. Agolf ball according to claim 8, wherein the inner core layer has asurface Shore D hardness of from about 45 to about
 55. 11. A golf ballaccording to claim 8, wherein the outer core layer has a surface Shore Dhardness of from about 50 to about 60 and is higher than the surfacehardness of the inner core layer.
 12. A golf ball according to claim 1,wherein the inner core layer has a Shore D cross-sectional hardness offrom 45 to 55 at any single point on a cross-section obtained by cuttingthe inner core layer in half, and has a Shore D cross-sectional hardnessdifference between any two points on the cross-section of within ±6. 13.A golf ball according to claim 1, wherein the sphere comprising theinner core layer enclosed by the outer core layer has a coefficient ofrestitution of at least about 0.8.
 14. A golf ball according to claim 1,wherein the intermediate layer has a surface Shore D hardness of atleast about 60 and the cover layer has a surface Shore D hardness offrom about 45 to about
 60. 15. A golf ball according to claim 1, whereinthe intermediate layer comprises a thermoplastic material comprising atleast one of an ionomer resin, a highly neutralized acid polymer, apolyamide resin, a polyurethane resin, and a polyester resin.
 16. A golfball according to claim 1, wherein the unsaturated diol (a) istrimethylolpropane monoallylether.
 17. A golf ball according to claim 1,wherein the cover layer has a flexural modulus of less than 1,000 psi.18. A golf ball according to claim 1, wherein the intermediate layer isan inner cover layer.